The research has focused on multiple myeloma, a B-cell malignancy. Career goals are to expand knowledge of B-cell neoplasia to include non-Hodgkin's lymphoma (NHL) and to use training in laboratory science to study molecular markers of exposure. To obtain the training and experience needed to become an independent investigator with emphasis in these areas, it is planned to: 1. Audit Immunology and Molecular Epidemiology courses at Stanford University; 2. Write a review article on the epidemiology of NHL subtypes; 3. Use existing computerized data to investigate the demographic occurrence of NHL subtypes, and the role of smoking and HIV infection in NHL; and, 4. Write a methodological article outlining design trade-offs to minimize information bias in epidemiologic research using laboratory-based measurements. A major strength of conducting research at Kaiser Permanente stems from the long-term follow-up of patients. Prospective information on physical and medical characteristics can be quickly obtained from the medical record. It is proposed to take advantage of this strength and collect original data to evaluate two hypotheses: 5. Is relatively tall height-for-age in girls aged 8 to 18 years associated with the subsequent risk of epithelial breast cancer? 6. Does surgical correction of cryptorchidism (orchidopexy) at a relatively young age reduce the risk of germ-cell testicular cancer to a greater extent than if the correction is made later?